1. Field of the Invention
The present invention relates to a charged particle beam irradiation method for applying a charged particle beam to a sample, and to a charged particle beam apparatus. In particular, the invention provides a method for detecting information concerning an electric potential on a sample, which is preferable for measuring an electric potential on a sample, and a charged particle beam apparatus for detecting an electric potential on a sample.
2. Background Art
Recently, with the advancement of semiconductor devices, the importance of semiconductor measurement and test technology has been increasing. A scanning electron microscope, which is typified by a CD-SEM (Critical Dimension-Scanning Electron Microscope), is an apparatus for measuring a pattern formed on a semiconductor device by scanning a sample with an electron beam, and detecting electrons (such as secondary electrons) emitted from the sample. In such apparatus, it is necessary to set proper apparatus conditions to perform highly-accurate measurements and tests. Some samples of recent devices become electrically charged due to electron beam irradiation or the influence of semiconductor processing. More specifically, insulating samples, such as a resist, an insulating film or a low-k material, are known to be easily charged.
When a sample is electrically charged, the electron orbit is distorted, which may cause astigmatism or image blurring. JP Patent Publication (Kokai) No. 4-229541 (Patent Document 1), JP Patent Publication (Kokai) No. 10-125271 (Patent Document 2), and JP Patent Publication (Kokai) No. 2001-236915 (Patent Document 3) each describe a technique for measuring the charge quantity on such an electrically charged sample and controlling a voltage applied to the sample so as eliminate the influence of the charge in order to properly perform focusing on the sample.
Also, JP Patent Publication (Kokai) No. 1-214769 (Patent Document 4) describes a technique for detecting field emission current emitted from a metal needle with a sharp tip or tunnel current in order to contactlessly measure the potential on a sample.